Waste to energy direct carbon fuel cell development with lanthanum strontium calcium titanate based anode

Abstract

Perovskite-based material La_0.2Sr_0.25Ca_0.45M_xTi_1-xO_3-δ (M=Fe, Co, Ni) was synthesised successfully using optimised Pechini method. SOFC system was fabricated using the synthesised material as the anode, YSZ as the electrolyte, and LSM as the cathode. Initial evaluations were conducted with hydrogen as the fuel. Electrochemical switching in humidified hydrogen is found to significantly improve the performance of the cells. Hydrogen SOFC with La_0.2Sr_0.25Ca_0.45Co_0.025Fe_0.025Ti_0.95O_3-δ anode is found to show low polarisation resistance (3.23 Ω/cm²) and high maximum power density (227 mW/cm²).

HDCFCs were setup with the fuel mixture containing eutectic K₂CO₃/Li₂CO₃ and activated charcoal. When purged with N₂, performance of HDCFCs was found inferior to that of hydrogen SOFCs. Better performance was observed with CO₂ as the purging gas. For example, in CO₂, HDCFC with La_0.2Sr_0.25Ca_0.45Co_0.025Fe_0.025Ti_0.95O_3-δ anode showed a polarization resistance of 2.31 Ω/cm² and power density of 99.6 mW/cm².

To explore the waste-to-energy applications of HDCFCs, medium density fibreboard was pyrolysed, forming a biochar with high oxygen content. Using this biochar as the fuel in the HDCFCs, unexpected OCV loss was observed for high operation temperatures when purged with N₂. With the limitation in testing temperature, worse performance was observed. CO₂ purging maintained OCV at higher temperatures, with the La_0.2Sr_0.25Ca_0.45Co_0.025Fe_0.025Ti_0.95O_3-δ anode showing a polarisation resistance of 9.79 Ω/cm² and power density of 11.6 mW/cm².

Abnormal shape in the I-V curve was observed for HDCFCs and some of the SOFCs tested. In attempt to understand this observation, EIS at different applied voltages were obtained, various conditions were applied for the I-V scans, carbonate concentrations in the fuel mixture were tested and different voltages were applied to the HDCFCs while the off-gases were analysed using gas chromatography. Redox behaviour of anode materials under different applied voltages and the change in CO and carbonate concentrations are suggested to be related to the abnormal curve.

Date of Award	3 Jul 2025
Original language	English
Awarding Institution	University of St Andrews
Supervisor	John Thomas Sirr Irvine (Supervisor)